New Jersey Turnpike As a Power Source?

New Jersites writes "New Jersey, home of the eponymous Jersey barrier, is considering wind turbines powered by the breeze generated from traffic on the Jersey Turnpike. The wind turbines won't be built on the side of the highway. They will be built inside — what else? — the Jersey barriers. By replacing sections of solid concrete with Darius turbines, they might be able to harvest enough energy to power a light-rail line."

Drag?

[Graham MacRobie (1082093)]

I'm not a physicist, but won't the turbines cause a drag effect on the cars, resulting in the cars burning more fuel? Is so, aren't they just moving the problem from one place to another? There's no such thing as free energy, right?

Truly curious - I'd love an explanation if someone knows why this isn't the case.

Re:Drag?

[Rei (128717)]

Yeah. Without the extra drag from the turbines, that "breeze" would be reducing drag on the cars. They're basically using cars as generators. Brilliant strategy there, given how inefficient ICEs are.
 

Re:Drag?

[dbIII (701233)]

Yes, insightful for a given value of insight - however moving the turbines a short distance away from the things instead of doing something stupid will give you both the wind to spin the turbines and no extra drag on the vehicles. Ducting is also possible to get a lot of wind to the turbines if they are far away without reflecting much back on to the vehicles.

I know it's not exactly high school stuff but if you think of it as simple 2D water flow it still is not difficult - the ripples from an obstruction only travel a finite distance upstream.

Re:Drag?

[arivanov (12034)]

Absolutely. This is not a free energy at all. What I find more interesting is that the system uses the same turbine design as Quiet Revolution turbines. AFAIK this design is still under a couple of patents so they will have to shell out a very sizeable license fee. Pity Quiet Revolution is not public, this would have been a good time to play with its shares.

Re:Drag?

[Alioth (221270)]

Not quite.

The air moved around by the cars is being absorbed and dissipated anyway by the objects surrounding the road. All the turbines will do is instead of the airflow from the cars going to swish the surrounding grass, trees and bushes - it'll spin a turbine. The energy is already being absorbed by the surrounds of the road.

It's like putting a turbine over a kettle - you won't cause the kettle to use more energy to boil the water by allowing the steam coming from it to pass through a turbine - you'll just extract some of the energy that otherwise would have been used up by the environment of the kettle.

If it's designed correctly, it won't increase drag.

Re:Drag?

[deek (22697)]

I'm not a physicist, but won't the turbines cause a drag effect on the cars, resulting in the cars burning more fuel?

You've got it right. The turbines would take energy from the air being pushed around by the cars, leading to the breeze around the car slowing down, and therefore exerting more drag on the car.

At the same time, this is a rather ingenious way of creating a virtual toll for roads. If the power gathered is then invested into a public transport system, then you'll end up having drivers subsidise public transport. The fuel savings with public transport may well offset the extra fuel burnt through the turbine induced drag.

Re:Drag?

[Myself (57572)]

The wind blowing on that unit isn't caused by the cars, and that wind doesn't always benefit the cars.

The wind in the (been-shot-down-before) turnpike story is a draft caused by the cars' motion, and benefits their efficiency because it acts like a slight tailwind for each vehicle. Eliminating that tailwind would have a large energy cost, compared to the minor harvest from the turbines.

Drag's not the full story.

[EmbeddedJanitor (597831)]

The energy must come from somewhere, so it must be ultimately coming from the gas powered car. However, if it is being taken in the right way it is energy that would otherwise be converted into waste heat/sound.

In other words, if the car drag is causing a wind of sorts, that wind would normally dissipate its energy as friction against the surfaces it blows along - causing the energy top be lost as heat. Now we're just providing an alternative energy soak that extracts the useful enrgy.

Re:Drag?

[smenor (905244)]

I am a physicist and had the same thought.

Without a doubt, the turbines will interfere with laminar flow, increase turbulence, and increase drag.

I have no idea if the increase in drag will dominate over the increase in efficiency by reclaiming lost energy, but it's definitely something that should be studied before implementing this kind of system on a large scale.

Yes: Drag.

[Ungrounded Lightning (62228)]

But the cars are the wind generators, not the turbines. If a turbine generated any significant wind itself, then it wouldn't be a very effective generator, would it?

The stream of cars generates an air motion along their path. Like geese (though through a different mechanism) the leading cars reduce the amount of air drag experienced by following cars. This improves their fuel economy. (The phenomenon is even more pronounced with semi-trucks. "Drafting": following another truck closely to save even more fuel, is a common practice.

A smooth central barrier separating the two directions of traffic improves the situation by letting the two sides of the freeway have separate airstreams traveling in opposite directions. The barrier reduces energy lost to turbulence, improving the airflow.

Replacing the barrier with turbines will suck energy out of the air streams on both sides to generate electricity. The result will be to decelerate the airstreams that had been giving following vehicles an advantage.

While some of the power comes from captured crosswinds and some from capturing energy that would have been lost to turbulence anyhow, a large portion of it comes from increasing the drag on following vehicles by putting friction on the "following wind": Fuel economy for the trailing vehicles in a bunch is reduced to something near that of lone or leading vehicles.

But there's plenty of power to be had higher

[Ungrounded Lightning (62228)]

By the way:

There's PLENTY of power to be had WITHOUT disrupting the traffic airflow and canabalizing the fuel of the cars.

A freeway or toll road is a clear area and there will be plenty of winds ABOVE it that are essentially unrelated to the airflow near the ground. They're also faster - with energy going up with the CUBE of the airspeed.

By building a wind turbine that starts significantly above the ground the turbines can avoid disturbing the flow at traffic level while collecting plenty of energy.

Also: A Darrieus wants linear airflow THROUGH it. It would be great for salvaging power from crosswind, but rotten for snagging power from opposing winds on the two sides of its axes.

And they're a major hazard: Darrieus turbines fly at tip speeds of about 7 times the wind speed and their narrow blades experience drag loads about equivalent to a wind barrier with a cross-section the size of the swept area - reversing twice per rotation. This has tended to produce fatigue in their materials, sometimes ending with the mill coming apart in high winds some years after construction, with massive pieces flying around at a goodly fraction of the speed of sound.

A savonius-derived design (like the Sandia configuration) would be a better choice. Though it only collects about 2/3s as much power for a given swept area, it rotates at about an eighth the speed and has broad blades that can be much more solidly constructed.

Re:Yes: Drag.

[Bastard of Subhumani (827601)]

The phenomenon is even more pronounced with semi-trucks. "Drafting": following another truck closely to save even more fuel, is a common practice.

I assume this aerodynamic phenomenon miraculously turns into a cushion in the event that the truck in front has to stop real damn quick?

Re:Drag?

[WrongSizeGlass (838941)]

A better idea would be to try to harness the anger and frustration of those of us who drive the NJ Turnpike. You could really support the power grid with all that wasted energy.

Re:Drag?

[name*censored* (884880)]

>>A better idea would be to try to harness the anger and frustration of those of us who drive the NJ Turnpike. You could really >>support the power grid with all that wasted energy.

>>but won't the turbines cause a drag effect on the cars, resulting in the cars burning more fuel? Is so, aren't they just >>moving the problem from one place to another? There's no such thing as free energy, right?

Putting two and two together.. wouldn't harnessing the anger make people ANGRIER? There's no such thing as free anger!

Finally...

[ZiakII (829432)]

Finally something I have to be proud about in NJ besides the Devils....

yawn

[User 956 (568564)]

y replacing sections of solid concrete with Darius turbines, they might be able to harvest enough energy to power a light-rail line.

That's boring. Wake me up when they can power a light rail gun.

Why's the train not running?

[rmadhuram (525803)]

Oh wait, there's a traffic jam!

The barriers are supposed to be solid.

[deopmix (965178)]

This might work until somebody decides to use the barriers for their original purpose(separating traffic). When the Powers That Be realize that the only thing separating two lanes of traffic moving at each other at 140 mph is a few turbines they may decide that this is a Bad Idea.

Re:The barriers are supposed to be solid.

[mrchaotica (681592)]

I wouldn't be worried about the turbines failing to separate the cars (assuming they were built solidly); I'd be worried about cost. Jersey barriers are surely much cheaper and more durable than turbines, and I think the cost of turbine repair or replacement after the inevitable accidents would be enough to make this proposal uneconomical.

An excuse for speeding...

[xrapidx (615195)]

...this will create a good excuse when pullled over for speeding . You were only trying to do your part to power the light-rail line.

"New" Jersey Barriers

[Akron (799321)]

Before everyone decides to start bashing good ole NJ. I would like to point out that the actual article says nothing about the NJ Turnpike. The current concrete barriers are called Jersey barriers, and all we have here is a new barrier with turbines...thus the name "NEW" Jersey Barrier.

Dumb idea - way too small

[Animats (122034)]

Wrong answer. Too many little turbines not generating enough energy each. Worse, gearing a number of turbines together when they don't get uniform wind pressure means some of them are just sources of drag.

Progress in wind turbines has been through scaling them up. The 50KW - 100 KW machines of the 1970s never paid for themselves. Somewhere above 500KW, the economics start to work, and farms of megawatt and up machines are quite profitable. Here's General Electric's 2.5 megawatt wind turbine, [gepower.com] which is typical of current large wind turbines. Total worldwide wind generation capacity is about 75 gigawatts. Wind power is now a serious energy source because, at last, the units are big enough to generate serious power.

Rediculus

[rizole (666389)]

As has been pointed out already this is a stupid idea. It would make much more sense to put the turbine on the train so it's forward motion can generate electricity. That way the train is self powering. Much greener.

Newsflash!

[fury88 (905473)]

"Tonight at 11. Commuters leave roadways to ride new rail. Not enough power to run the rail."

television remote power source ..

[rs232 (849320)]

If they banned television remotes and wired everyones couch to the grid, then every time someone got up to change the channel they would generate power.